Europol’s chief warned that encrypted online communications services are the biggest problem for security agencies tackling terrorism, thus joining an ever-growing list of security officers troubled by this issue.
The chief of European police intelligence agency Rob Wainwright told the BBC that hidden areas of the Web and encrypted communications make it harder to monitor terror suspects.
With these comments he joins FBI director James Comey, former European Cyber Crime Centre head Troels Oerting and GCHQ director Robert Hannigan, who have all made similar statements.
"We are disappointed by the position taken by these tech firms and it only adds to our problems in getting to the communications of the most dangerous people that are abusing the internet,” he said.
"Tech firms are doing it, I suppose, because of a commercial imperative driven by what they perceive to be consumer demand for greater privacy of their communications."
A spokesman for TechUK, the UK's technology trade association, underlined the need to resolve the tension between privacy and national security because the security of digital communications underpins the UK economy.
"Encryption is an essential component of the modern world and ensures the UK retains its position as one of the world's leading economies,” a TechUK spokesman told the BBC.
Wainwright acknowledged that all of this was a result of Edward Snowden’s discoveries, which unveiled that governments could monitor anyone’s phone calls, messages, e-mails, as well as other online activity.
He said security agencies now had to work to rebuild trust between technology firms and the authorities.